Become a Member: Get Ad-Free Access to 3,000+ Reviews, Guides, & More

Mineral or synthetic oil for your motorcycle?

oil break in motorcycle

This age-old question about oils doesn’t have an easy answer.

However, your motorcycle manual will specify a particular oil. Some even suggest one type of oil for the run-in stage and another for ongoing use.

It is prudent to adhere strictly to what is suggested. But usually the manual only provides specifications of viscosity/weight and service classifications, not the origin or the manufacturer.

Synthetic oils are manmade, consistent and devoid of contaminants, while mineral oils come from the ground and, although being refined, can contain some contaminants.

But does that mean you should only use synthetic oils? Not really. The mineral oil refining process is very thorough. Any contaminants will be miniscule and unlikely to do damage. Besides, some synthetic oils actually use mineral oils as part of their formula.

The main advantage of mineral oils is that they are cheaper, sometimes about a quarter of the price of synthetics. Many new motorcycles are delivered with mineral oil in them. That’s not necessarily a cost-saving measure. Mineral oil actually helps the rings and pistons bed in properly during the crucial run-in stage. Synthetic oils can create a film around the bore so it doesn’t seal properly, leading to slippage and higher oil use later in the engine’s lifespan.


fake products oilMineral oils are also more suitable for older motorcycles because they are heavier or thicker and don’t leak. Owners who change to synthetic oils in older motorcycles often find they leak more.

But be aware that older bikes specify the type of oil that was available at the time they were built and those oils may not be available anymore. However current generation oils will be far better than what was originally specified for older applications.

Will an older bike benefit from an expensive synthetic oil as opposed to a current generation mineral oil? Probably not, as older engines (unless modified) are unlikely to be that highly stressed that they would benefit from a synthetic.

Will it do any harm?  Providing viscosity ratings are appropriate – probably not, except to your wallet!

As for modern motorcycles, most mechanics believe synthetic oil is best, especially after the first service.

There are many advantages of synthetic oils, including the fact that they are better able to properly lubricate and tolerate the extremes the oils are subjected to in modern high-performance, high-revving engines. especially when operating in hot climates.


Synthetic oils also last longer which you will see for yourself when you drain the sump at your scheduled next service. Synthetic oil usually doesn’t form such a thick, black sludge caused by oxidation.

But don’t be alarmed if the drained oil is dirty. That’s just the oil doing its job. If it comes out looking the same as it went in, you might have a problem as it’s not doing its job.

The lower viscosity (resistance to breaking down) of synthetic oils reduces internal friction which means better efficiency, more performance and slightly higher fuel economy.

It may cost a lot more than mineral oil, but it may yield some economic returns in fuel economy, a longer-lasting engine and longer periods between oil changes. However, extending your scheduled oil change would be a false economy in the long run.

Lane filtering
Bike fan Steve Spalding

RACQ technical officer Steve Spalding advises that owners should use quality branded oil and keep to the schedule for oil and filter changes as motorcycle engines place high demands on engine oils. Air-cooled engines, in particular, place a lot of stress on the oil in hot weather and stop-start traffic conditions. (Check these tips on finding the best car oil filters.)

“In my experience, a good quality synthetic oil is a small price to pay for engine protection.

I learnt from experience when I first started riding in the late ’70s that the wrong oil can be costly. After pulling into a service station one night I filled my 250 Yamaha with auto transmission fluid instead of two stroke oil because I wasn’t paying attention, even though the oil was the typical dark red colour. Within a day of further riding the engine seized and it cost me barrels, pistons, secondhand crank and rods plus a few very late nights rebuilding the engine.”


And then there’s two-stroke engines: It’s fairly basic quality because it gets burnt but it’s designed to have low smoke emissions and limited combustion chamber deposits.  It definitely isn’t the same as oil used in a four-stroke engine.

Also oils for wet clutches are specific to avoid the potential for clutch slip. The Japan Lubricating Oil Society (JASO) provides specifications for petrol engine oils which are particularly relevant to motorcycles and other small engines. There are specific standards for two-stroke engines, for example JASO FC or FD, and for four-stroke engines (JASO MA and MA2), such as those used in motorcycles which have a clutch and gearbox that are also lubricated by the engine oil.

If this debate about mineral versus synthetic oils leaves you scratching your head, you can always opt for the compromise of semi-synthetic oils. It’s best to speak to your mechanic about what il best suits your needs.

  1. Actually this is inaccurate, ALL oil comes from the ground, “synthetic” is a marketing term. Basically ALL oils are manufactured from a “Base oil” component. The purity of this base determines the ultimate quality of the oil. All oils have additives added to this base which determines its intended use.

    semi-synthetic oils is again a marketing term and is basically a waste of money, Either buy a plain “mineral” oil or “synthetic”

  2. I own a 1982 Kawasaki KZ1100 Shaft. It has 12,000 miles on the odometer.
    Standard motorcycle oil is best I’m sure but do you recommend a particular brand ?
    I’m also in a mild/hot climate in Tampa Fl.


  3. Group 3 synthetics are hydrocracked mineral oils. Synthetic in this case is a marketing term. Group 4 and 5 oils are PAO and Ester based oils, and are a proper synthetic oils.
    Personally, I don’t think you can go wrong if you stick to good name brands, with the correct API rating; the correct viscosity rating, use the chart in your manual to fine tune viscosity to ambient climatic conditions; the correct JASO ratings i.e. MA for wet clutches.
    I use a full synthetic Castrol oil. It happens to be the one recommended for my bike by the manufacture, but it also happens to appear on special at a very good price in my local store.
    True synthetics are harder wearing oils. They don’t require Viscosity Index improvers to achieve the multigrade properties, and it is these VI improvers that break down at high revs and heat cycles, that cause the accelerated viscosity loss experienced in mineral based oils.

  4. Just a comment on the synthetic oil in a older bike. My 1982 Kawasaki has a wet clutch and the synthetic caused it to slip pretty badly. I am sure the synthetic would have been better for the engine but not so for the clutch.

    1. Make sure the fully synthetic has JASO MA on the oil container otherwise it will have engine efficiency additives for cars that make the wet clutch slip. Non JASO MA oils are unsuitable for motorcycles. IMHO the age of the clutch is more likely the problem than the oil in it and the oils used at the time of manufacture have changed dramatically

  5. Full synthetic are ester based oil have nothing to do with mineral oil. Semi are like it says a mix between mineral oil and additives to make it last longer … mineral is the oil I would never recommend in a high performance engine because it breaks down easily with higher temperatures and loses its viscosity ratings.

    Personally I use a full synthetic oil in my motorcycle and I’ve never experienced any issues with the clutch whatsoever and the longevity of the engine is what matters to me most.

    I choose to pay a premium price for the best lubrication and protection for my engine.

    I specifically didn’t write any brand or oil tupe since I don’t want to start a fire 😉

  6. As for clutch slippage, this is a component of the additive package rather than the oil being synthetic or mineral based. The easiest way to ensure that the oil will be OK in a wet clutch is to check if the oil carries a JASO MA rating. So along with checking that the oil meets the API rating and viscosity rating, you should check for the JASO rating if you have a wet clutch.

  7. Great article, I have done 280,000kms on a gs1100, 240,000 on a gsx1100g, 180,00 on a k100 and 135,000 on my current FZ1. All done in mineral oil, no breakdowns, always changed at 3000 to 4000 kms. I would suggest older air cooled and higher mileage bikes 20w50 mineral, if nothing else it seems to make much tighter gear changes, with less clunk, especially in Yamahas. (and of course with positive pressure on gear changes) If I bought a new R1 I would run synthetic after the run in period (which I was told is closer to 20,000kms ) by a Yamaha engineer

  8. My bike is a 2003 Honda VTR250 with wet clutch, which has been run for nearly 50km so far.
    Currently,I am using full synthetic oil for the whole system including engine and transmission.
    Who can tell me what type of oil, say mineral or synthetic,that would be more suitable for my bike with regards to performance and reliability.

Comments are closed.